YIELD PERFORMANCE AND ECONOMIC RETURN OF MAIZE AS AFFECTED BY NUTRIENT MANAGEMENT STRATEGIES ON FERRALSOLS IN COASTAL WESTERN AFRICA

We assessed maize (Zea mays L.) grain yield and associated economic returns of four soil fertility management strategies in a 2-yr study (four growing seasons). The Ikenne maize cultivar was used and the fertilization treatments included: no fertilizer application (control, T1), application of farmyard manure (FYM) at the rate of 6 Mg ha-1 (T2), the agricultural services recommended maize-based fertilization consisting of 200 kg N15P15K15 plus 100 kg urea (46% N) ha-1 (T3) and application of 3 Mg of FYM plus 100 kg N15P15K15 plus 50 kg urea (46% N) ha-1 (T4). On the 2-yr period basis, four-season cumulative grain yields under T4, T3 and T2 were 40, 25 and 22% higher as compared with T1, respectively, those under T4 and T3 were 15 and 3% higher as compared with T2, respectively, while the yield under T4 was 12% higher than that under T3. For the 2-yr period, on a per hectare basis, economic profits under T4, T3 and T2 were 69 and 31% higher and 10% lower as compared with T1, respectively, profits under T4 and T3 were 87 and 46% higher as compared with T2, respectively, while profit under T4 was 28% higher than that under T3. In the current context of degraded soils in coastal western Africa, T4 reflecting a combined application of mineral fertilizer at the rate of N38P15K15 ha-1 plus organic amendment as FYM at the rate of 3 Mg ha-1 should be advised towards sustaining enhanced maize crop productivity and profitability

Fertiliser requirements for balanced nutrition of cassava across eight locations in West Africa

Insufficient and unbalanced fertiliser use widens cassava yield gaps. We assessed the spatial variability of optimal fertiliser requirements of cassava for enhanced nutrient use efficiency and increased yield using the balanced nutrition approach of the QUEFTS model. Two datasets comprised of five fertiliser experiments conducted at eight locations across Southern Togo, Southern Ghana and Northern Ghana from 2007 to 2012 were used. The ratio of storage roots dry matter yield over the sum of available N, P and K expressed in crop nutrient equivalent from the soil and nutrient inputs was used as a proxy to estimate nutrient use efficiency. Nutrient use efficiencies of 20.5 and 31.7kg storage roots dry matter per kilo crop nutrient equivalent were achieved at balanced nutrition at harvest index (HI) values of 0.50 and 0.65, respectively. N, P and K supplies of 16.2, 2.7 and 11.5kg at an HI of 0.50, and 10.5, 1.9 and 8.4kg at an HI of 0.65 were required to produce 1000kg of storage roots dry matter. The corresponding optimal NPK supply ratios are 6.0-1.0-4.2 and 5.3-1.0-4.2. Nutrient use efficiencies decreased above yields of 77-93% of the maximum. Evaluation of the performance of blanket fertiliser rates recommended by national research services for cassava production resulted in average benefit:cost ratios of 2.4±0.9, which will be unattractive to many farmers compared to 3.8±1.1 for the balanced fertiliser rates. The indigenous soil supply of nutrients revealed that, at balanced nutrition, K was the most limiting nutrient to achieve storage roots yields up to 8Mg dry matter ha-1 at most sites, whereas N and P were needed at greater yields. Dry weight of storage roots measured on the control plots in our researcher managed experiment ranged from 5.6 to 12.2Mgha-1, and were larger than the average weight in farmers' fields in West Africa of 4Mgha-1. Substantial yield increase could be attained in the region with improved crop management and fertiliser requirements formulation on the basis of balanced nutrition.</p

Gestion efficiente des nutriments en riziculture irriguee dans la vallee de Zio avec differentes formes d’engrais mineraux

Maximiser l’efficience d’utilisation des nutriments en culture irriguée est une condition pour la création de la résilience agricole aux changements climatiques. Nous avons évalué pendant deux cycles de culture l’effet de la fertilisation minérale sur le rendement et la rentabilité économique en riziculture irriguée pour identifier des stratégies optimales de gestions des nutriments. Quatre traitements de fertilisants ont été utilisés : F1 (sans engrais), F2 (200kg N15P15K15+ 100kg d’urée perlée ha-1), F3 (200 kg N15P15K15 + 100kg Urée Super Granulé ha-1) et F4 (N76 P30 K30 en engrais simples TSP, KCL, USG). Deux variétés de riz (IR841 et NERICA L14) ont été utilisées en split-plot à trois répétitions sur le périmètre de la vallée de Zio entre mai 2015 et Mars 2016. Pour IR841, les rendements moyens sous F4 et F3, ont été respectivement de 118.09%, 99.41 % supérieur à F1 (2.57 Mg.ha-1). La F2 n’a permis que 3.53Mg/ha de paddy. Pour le NERICA L14, par rapport à F2 qui a donnée 4.44 Mg ha-1 les stratégies F3 et F4 ont permis des augmentations respectives de 40.20% et 51.68%. La marge brute a été de 165 800 et 301 400 F CFA pour IR841 et NERICA L14 sous F4 et presque similaire sous T2 (151 120 et 281 920 F CFA pour IR841 et NERICA L14). F2 a donné une marge brute négative avec la variété IR841. Les rendements de NERICA L14 ont été supérieurs à ceux de l’IR841. L’USG a permis donc d’améliorer les rendements et la profitabilité de la culture de riz dans la vallée de Zio. Mots clés : Gestion de nutriments, Rendement, profitabilité, engrais minéraux, riz

Modelisation des doses economiques optimales du fumier de ferme en culture du maïs (Zea mays L.) sur les sols ferrallitiques au Togo

La combinaison de fertilisants minéraux et organiques est la meilleure approche de fertilisation du maïs. Cependant, en Afrique occidentale, la faible accessibilité aux engrais minéraux contraint parfois à utiliser exclusivement des fertilisants organiques. Malheureusement, la recommandation de fumure organique établie dans les années 1980 est unique, indépendante de la diversité des sols, des systèmes de production et des fertilisants organiques disponibles. Il s’avère nécessaire de déterminer et d’actualiser régulièrement les doses économiques optimales des fertilisants organiques couramment disponibles. La réponse du rendement en grain du maïs (variété Ikenne) à la dose de fumier a été modélisée à partir de deux essais conduits à Lomé suivant un dispositif en blocs aléatoires complets, sur sol ferrallitique, sous climat tropical guinéen à quatre saisons. Cinq doses de fumier (3000, 6000, 9000, 12000 et 15000 kg ha-1) ont été étudiées sur deux saisons en 2016. Les modèles quadratiques obtenus ont servi à déterminer les doses économiques optimales. En grande saison, la dose économique optimale du fumier a été de 8530 kg ha-1 pour le premier essai et de 9130 kg ha-1 pour le deuxième essai. En petite saison, la dose économique optimale du fumier a été 7810 kg ha-1 pour le premier essai et de 8280 kg ha-1 pour le deuxième essai. La recommandation en vigueur pour l’amendement organique des sols (6000 kg ha-1) devraient être révisées et adaptées aux différents systèmes de production.Mots clés : Maïs, dose économique optimale, fumier de ferme, sol ferrallitique

Long-term mineral fertiliser use and maize residue incorporation do not compensate for carbon and nutrient losses from a Ferralsol under continuous maize-cotton cropping

It has been repeatedly argued that mineral fertiliser application combined with in situ retention of crop residue biomass can sustain long-term productivity of West African soils. Using 20-year experimental data from southern Togo, a biannual rainfall area, we analysed the effect of two rates of mineral NPK fertiliser application to maize-cotton rotation on the long-term dynamics of soil C and nutrient contents, as compared with two control treatments. Mineral fertiliser treatments consisted of application to both maize (first season) and cotton (second season) the research-recommended NPK rates (Fertiliser-RR) and 1.5 times these rates (Fertiliser-1.5 RR). Control treatments consisted of cropping maize and cotton without fertiliser use (No-Fertiliser) and of double annual soil tillage (as done for planted treatments) without planting a crop (Tillage-NoCrop). Maize residue biomass was every year returned to the soil of crops planted treatments, whereas cotton stems were uprooted, piled and burnt on the experimental plots as done locally for phyto-sanitary reasons. Treatment effects were analysed through a long-term change in crop productivity, in soil C and nutrient contents. Our results indicate that productivity of maize and notably of cotton cannot be sustained in this Ferralsol without nutrient inputs. On average, maize yields without fertilisers decreased from 2tha-1 after woodland clearing to 0.5tha-1 after 10 years of cultivation, while cotton yields decreased from 1.5 to 0.5tha-1 only after 5 years. In spite of the need of mineral fertiliser use to sustain productivity of this soil, there was little justification to increase inputs of mineral fertiliser over the research recommended rate. Over 20-year experiment, both maize and cotton while received N, P and K inputs at the research-recommended rates produced virtually the same yields as when these rates were increased by 50%. Although C inputs to soil under RR and 1.5 RR were greater than in the No-Fertiliser control (nil for Tillage-NoCrop), and the N input was more favourable for 1.5RR, the rates in which contents of soil C and N decreased over time did not differ substantially between treatments. Soil available P decreased for all treatments, while exchangeable K concentration increased under RR and 1.5 RR and decreased in unfertilised treatments (No-Fertiliser and Tillage-NoCrop). In fertilised plots and in tillage no-planted plots, soil pH decreased more than in No-Fertiliser plots. A decline of soil pH was associated with a decline of exchangeable Ca and Mg, which were on average 20 and 40% higher in fertilised plots than in No-Fertiliser plots. We conclude that soil C and N decline in this Ferralsol was more determined by a change in soil conditions due to woodland clearance and continuous tillage than by the quantities of C or N inputs added annually.</p

Long-term mineral fertiliser use and maize residue incorporation do not compensate for carbon and nutrient losses from a Ferralsol under continuous maize-cotton cropping

Article in pressIt has been repeatedly argued that mineral fertiliser application combined with in situ retention of crop residue biomass can sustain long-term productivity of West African soils. Using 20-year experimental data from southern Togo, a biannual rainfall area, we analysed the effect of two rates of mineral NPK fertiliser application to maize–cotton rotation on the long-term dynamics of soil C and nutrient contents, as compared with two control treatments. Mineral fertiliser treatments consisted of application to both maize (first season) and cotton (second season) the research-recommended NPK rates (Fertiliser-RR) and 1.5 times these rates (Fertiliser-1.5 RR). Control treatments consisted of cropping maize and cotton without fertiliser use (No-Fertiliser) and of double annual soil tillage (as done for planted treatments) without planting a crop (Tillage-NoCrop). Maize residue biomass was every year returned to the soil of crops planted treatments, whereas cotton stems were uprooted, piled and burnt on the experimental plots as done locally for phyto-sanitary reasons. Treatment effects were analysed through a long-term change in crop productivity, in soil C and nutrient contents. Our results indicate that productivity of maize and notably of cotton cannot be sustained in this Ferralsol without nutrient inputs. On average, maize yields without fertilisers decreased from 2 t ha?1 after woodland clearing to 0.5 t ha?1 after 10 years of cultivation, while cotton yields decreased from 1.5 to 0.5 t ha?1 only after 5 years. In spite of the need of mineral fertiliser use to sustain productivity of this soil, there was little justification to increase inputs of mineral fertiliser over the research recommended rate. Over 20-year experiment, both maize and cotton while received N, P and K inputs at the research-recommended rates produced virtually the same yields as when these rates were increased by 50%. Although C inputs to soil under RR and 1.5 RR were greater than in the No-Fertiliser control (nil for Tillage-NoCrop), and the N input was more favourable for 1.5RR, the rates in which contents of soil C and N decreased over time did not differ substantially between treatments. Soil available P decreased for all treatments, while exchangeable K concentration increased under RR and 1.5 RR and decreased in unfertilised treatments (No-Fertiliser and Tillage-NoCrop). In fertilised plots and in tillage no-planted plots, soil pH decreased more than in No-Fertiliser plots. A decline of soil pH was associated with a decline of exchangeable Ca and Mg, which were on average 20 and 40% higher in fertilised plots than in No-Fertiliser plots. We conclude that soil C and N decline in this Ferralsol was more determined by a change in soil conditions due to woodland clearance and continuous tillage than by the quantities of C or N inputs added annuall

ARPN Journal of Agricultural and Biological Science ECONOMICS OF COMBINING ORGANIC AND IN-ORGANIC FERTILIZERS FOR MAIZE PRODUCTION UNDER TWO TILLAGE SYSTEMS IN THE NORTHERN SAVANNA ZONE OF GHANA

ABSTRACT Soils in the northern savanna zone of Ghana are poor in plant nutrients and are prone to compaction. Some amount of tillage and the application of fertilizers to enhance crop yields are necessary. The performance of maize on two tillage systems (Manual and bullock plough) with the application of different fertilizers was assessed for two years by a field experiment laid in a split-plot design with four replicates. The main plots were manual and bullock plough while the sub-plots were NPK (64 kg N/ha, 15 kg P205/ha and 15kg K20/ha), 6 tons/ha of animal manure, half the rate of in-organic and half the rate of animal manure and no fertilizer as the control in 2008 and 2009. The results showed that tillage loosened the soil and thus reduced soil bulk density, increased porosity and could have enhanced the availability of water and nutrients for better crop growth. The results further revealed that the application of animal manure alone increased maize yields in the second year by 57% as compared to 25% and 35% for the recommended fertilizer rates and half the rates respectively. However, maize yields from the recommended fertilizer rates and the half rates of both in-organic fertilizers and animal manure in each year were similar but significantly (p&lt;0.05) higher than the manure and the control treatment plots. The application of recommended in-organic fertilizers rates gave yields which were similar to yields obtained from half rates of the in-organic and animal manure but for sustainability, the combination of both could be recommended to farmers for adoption. Comparably, the net benefit-cost ratios of both tillage systems are more than 1 indicating that maize production on each of them is profitable; however the bullock tillage system is a better option as it had higher net benefit-cost ratios in each year than the manual system